EFFECTS OF ADMINISTRATION OF ADRENOCORTICOTROPIC HORMONE (ACTH) ON EXTRAGONADAL PROGESTERONE LEVELS IN SHEEP

To investigate the production of extragonadal progesterone and testost erone, Adrenocorticotrophic Hormone (ACTH) was administered to ovariec tomized ewes and wethers. In the first trial each animal received 2 ml of sterile saline (0.9%) iv. In the second trial, a week after the fi rst, animals were given 30 IU of ACTH iv. Blood samples were taken by venipuncture from the jugular vein for 8 h. The sampling interval was 30 min during the first 4 h and 60 min during the last 4 h. Treatments were applied after 2 h of sampling. Testosterone concentrations deter mined in the samples of the wethers in the ACTH trial were below the d etection limit of the assay in all cases. Administration of the saline solution did not affect hormone levels in any of the sexes. Cortisol concentrations (mean +/- SD) were 26 +/- 17 and 25 +/- 13 nmol/l, in e wes and wethers, respectively, and the corresponding progesterone conc entrations were 0.6 +/- 0.2 and 0.7 +/- 0.4 nmol/l. After ACTH adminis tration concentrations of both hormones were elevated for 2-3 h. Corti sol concentrations (mean +/- SD) were 219 +/- 68 and 276 +/- 90 nmol/l , in ewes and wethers, respectively. The progesterone concentrations f or the ewes and wethers were 1.1 +/- 0.5 and 3.5 +/- 2.4 nmol/l. These cortisol and progesterone levels differed significantly from pre-ACTH and saline-trial levels both in ewes and wethers. In wethers progeste rone was highly dependent on cortisol production (R-2 = 0.856; p = 0.0 010). In ewes no such relation between cortisol and progesterone was e vident (R-2 = 0.323; p = 0.1413).